I have a problem with pressure on my pressure gauge when my central heating is on the pressure goes to just comes under 3bar, if i raise the heating thermostat up the pressure goes beyond 3 bar and water drips from safety valve. The pressure gauge is normal at 1 to 1.5 bar when i am using d.hw the pressure remains same , it goes up when when my heating on. any suggestion whats wrong & how can i fix it.and also do i need to drain my boiler & heating system completely to put pressure in expansion vessel using foot pump .

NAT, May 2008

Easy job. Yes you need to depressurise the system, and then pump up the expansion vessel to 0.8 bar or so with a foot pump (and zero pressure on the front panel guage). Try pushing down the pin in the valve first, if a jet of water comes out you need a new vessel, if some dampness and a little air comes out it is fine. The expansion vessel is the big red thing behind the boiler and the valve is on top. Can be difficult to get at, depends on location.
Google for more info.
C.

c, May 2008

expansion vessel is f+*"ed. if boiler is hidden out the way (eg bigish cupboard), fit a remote vessel, cheaper, easier, does same job

zzzzzzzzzzz, May 2008